Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Biology > 2.1.3 Nucleotides and Nucleic Acids (Foundations in Biology) > Flashcards

2.1.3 Nucleotides and Nucleic Acids (Foundations in Biology) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What are nucleotides made of?

A
  • a pentose sugar
  • a nitrogenous base
  • a phosphate group
  • all nucleotides contain the elements C, H, O, N and P
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the roles of nucleotides?

A
  • form the monomers of nucleic acids: RNA and DNA
  • become phosphorylated nucleotides when they contain more than one phosphate group (e.g. ADP and ATP)
  • help regulate metabolic pathways e.g. ATP, ADP, AMO
  • components of some coenzymes e.g. NADP used in photosynthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the pentose sugar in a DNA nucleotide called?

A
  • deoxyribose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What varies on each DNA nucleotide and what stays the same?

A
  • the bases on each nucleotide may vary

- deoxyribose and the phosphate group stay the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the four possible bases called?

A
  • adenine (A)
  • thymine (T)
  • cytosine (C)
  • guanine (G)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What type of base are adenine and guanine?

A
  • purine base
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What type of base are cytosine and thymine?

A
  • pyrimidine base
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the structure of a purine base?

A
  • purine bases contain two carbon-nitrogen rings joined together
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the structure of pyrimidine base?

A
  • pyrimidine bases only have one carbon-nitrogen ring

- pyrimidine base is smaller than purine base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How many polynucleotide chains does a molecule of DNA contain?

A
  • two polynucleotide chains

- each chain is made up of lots of nucleotides joined together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where is DNA found?

A
  • in the nuclei in all eukaryotic cells

- found in the cytoplasm of prokaryotic cells and some viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the role of DNA?

A
  • the hereditary material

- carries coded instructions used in the development and functioning of all known living organisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is ADP and ATP?

A
  • phosphorylated nucleotides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do you phosphorylate a nucleotide?

A
  • you add one or more phosphate groups to it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does ADP and ATP contain?

A
  • the base adenine
  • the sugar ribose
  • two phosphate groups (diphosphate)
  • three phosphate groups (triphosphate)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the function for ATP?

A
  • provides energy for chemical reactions in the cell
  • ATP is synthesised from ADP and inorganic phosphate, using energy from an energy-releasing reaction e.g. the breakdown of glucose in respiration
  • the ADP is phosphorylated to form ATP and a phosphate bond is formed
  • energy is stored in the phosphate bond
  • when the energy is needed by a cell, ATP is broken back down into ADP and inorganic phosphate
  • energy is released from the phosphate bond and used by the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do nucleotides join together to form polynucleotides?

A
  • a condensation reaction between the phosphate group of one nucleotide and the sugar of another nucleotide
  • forming a phosphodiester bond (consisting of the phosphate group and two ester bonds)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the chain of sugars and phosphates known as?

A
  • the sugar-phosphate backbone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What bonds have to be break polynucleotides back into nucleotides?

A
  • the phosphodiester bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What type of bonding allows two DNA polynucleotide strands to join together?

A
  • hydrogen bonding between the bases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is complementary base pairing?

A
  • each base can only join with one specific other base to form the double helix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Which bases pair together and why?

A
  • Adenine (A) with Thymine (T)
  • Cytosine (C) with Guanine (G)
  • a purine always pairs with a pyrimidine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How many hydrogen bonds form between A and T?

A
  • two hydrogen bonds
24
Q

How many hydrogen bonds form between C and G?

A
  • three hydrogen bonds
25
Q

How do the polynucleotide strands form a DNA double helix?

A
  • two antiparallel (running in opposite directions) polynucleotide strands twist to form the DNA double-helix
26
Q

Why is the DNA double helix shape good?

A
  • compact
  • easy to break the H bonds and sugar phosphate backbone as they have a strong and stable structure
  • bases are protected in the middle
27
Q

How do you purify DNA using a precipitation reaction?

A
  • blend up your cells
  • make up a solution of detergent, salt and distilled water
  • add the broken-up cells into a beaker contains the detergent solution
  • incubate in a water bath at 60 degrees for 15 mins
  • then put the beaker in an ice bath to cool the mixture down
  • then filter the mixture and transfer a sample to a clean boiling tube
  • add protease enzymes to the filter mixture
  • some proteins will breakdown
  • slowly dribble some cold ethanol down the side of the tube, so it forms a layer on top of the mixture
  • after a few mins, DNA will form a white precipitate
  • remove this with a glass rod
28
Q

Why does DNA need to copy itself?

A
  • DNA copies itself before cell division

- so that each new cell has the full amount of DNA

29
Q

How does DNA replication work?

A
    • DNA helicase enzyme breaks the hydrogen bonds between the two polynucleotide DNA strands.
      - the helix unzips to form two single strands
    • each original single strand acts as a template for a new strand
      - free floating DNA nucleotides join to exposed bases on each original template by complementary base pairing (A with T, C with G)
    • the nucleotides of the new strand are joined together by the enzyme DNA polymerase
      - this forms the sugar-phosphate backbone
      - hydrogen bonds form between the bases on the original and new strand
      - the strands twist to form a double helix
    • each new DNA molecule contains one strand from the original DNA molecule and one new strand
30
Q

What type of copying is DNA replication and why?

A
  • semi-conservsation replication

- half of the strands in each new DNA molecule are from the original piece of DNA

31
Q

Why does DNA replication need to be accurate?

A
  • to make sure genetic information is conserved each time DNA in cell in replicated
32
Q

What is a mutation?

A
  • sometimes, a random, spontaneous mutation occurs
  • this is any change to the DNA base sequence
  • they can alter the sequence of amino acids in a protein and cause an abnormal protein to be produced
  • this abnormal protein may function better or not work at all
33
Q

What is a gene?

A
  • a sequence of DNA nucleotides that codes for a polypeptide
34
Q

What is a polypeptide?

A
  • the sequence of amino acids in a polypeptide forms the primary structure of a protein
35
Q

What makes each protein different?

A
  • different proteins have a different number and order of amino acids
36
Q

What determines the order of amino acids in a particular protein?

A
  • the order of nucleotide bases in a gene
37
Q

How many bases codes for each amino acid?

A
  • a sequence of three bases (called a triplet) codes each amino acid in a gene
38
Q

How are different amino acids made?

A
  • different sequences of bases code for different amino acids
39
Q

What is a template?

A
  • the sequence of bases in a section of DNA is a template that’s used to make proteins during protein synthesis
40
Q

Why does a section of DNA need to be copied into mRNA?

A
  • DNA molecules are found in the nucleus of the cell, but ribosomes that make proteins are found in the cytoplasm
41
Q

How many polynucleotide strands are there in RNA?

A
  • one

- it is a single polynucleotide strand

42
Q

What base does RNA contain instead of thymine and what base does it pair with?

A
  • uracil (U)

- to always pairs with adenine during photosynthesis

43
Q

What is messenger RNA (mRNA)?

A
  • made in the nucleus
  • three adjacent bases are called a codon
  • it carries the genetic code from the DNA in the nucleus to the cytoplasm, where it’s used to make a protein during translation
44
Q

What is transfer RNA (tRNA)?

A
  • found in the cytoplasm
  • it has an amino acid binding site at one end and a sequence of three bases at the other end called an anticodon
  • it carries the amino acids that are used to make proteins to the ribosomes during translation
45
Q

What is ribosomal RNA (rRNA)?

A
  • forms the two subunits in a ribosome (along with proteins)
  • the ribosome moves along the mRNA during protein synthesis
  • the rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids
46
Q

What is the genetic code?

A
  • the genetic code is the sequence of base triplets (codons) in DNA or mRNA, which codes for specific amino acids
47
Q

What are the three characteristic of the genetic code?

A
  • the genetic code is:
  • non-overlapping
  • degenerate
  • universal
48
Q

Why is the genetic code non-overlapping?

A
  • each base triplet is read in sequence, separate from the triplet before or after it
  • base triplets don’t share their bases
49
Q

Why is the genetic code degenerate?

A
  • there are more possible combination of triplets than there are amino acids (20 amino acids but 64 possible triplets)
  • this means some amino acids are coded for by more than one base triplet
50
Q

What are the stop or start codons?

A
  • some codons tell the cell when to start of stop production of the protein
  • found at the beginning and end of the gene
  • AUG is start codon
  • UAG is stop codon
51
Q

Why is the genetic code universal?

A
  • the same specific base triplets code for the same amino acids in all living things
52
Q

What is the definition of transcription?

A
  • the first stage of protein synthesis where a mRNA molecule is made from the template strand of DNA
53
Q

What is the definition of translation?

A
  • second stage of protein synthesis

- when the amino acids are assembled into a polypeptide

54
Q

Explain transcription

A

during transcription an mRNA copy of a gene is made in the nucleus:

  1. transcription starts when RNA polymerase (an enzyme) attaches to the DNA double-helix at the beginning of a gene
  2. the hydrogen bonds between the two DNA strands in the gene break, separating the strands and the DNA molecule uncoils at that point
  3. one of the strands is then used as a template to make an mRNA copy
    • RNA polymerase lines up free RNA nucleotides alongside the template strand
      - complementary base pairing means that the mRNA strand ends up being a complementary copy of the DNA template strand (except the base T is replaced by U in RNA)
  5. once the RNA nucleotides have paired up with their specific bases on the DNA strand, they’re joined together, forming an mRNA molecule
  6. the RNA polymerase moves along the DNA, separating the strands and assembling the mRNA strand
  7. the hydrogen bonds between the uncoiled strands of DNA re-form once the RNA polymerase has passed by and the strand coils back into a double helix
  8. when the RNA polymerase reaches a stop codon, it stops making mRNA and detached from the DNA
  9. the mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm, where translation takes place
55
Q

Explain translation

A
  • Translation occurs at the ribosomes in the cytoplasm
  • amino acids are joined together to make a polypeptide chain, following the sequence of codons carried by the mRNA
  1. the mRNA attaches itself to a ribosome and transfer RNA (tRNA) molecules carry amino acids to the ribosome
  2. a tRNA molecule, with an anticodon thats complementary to the start codon on the mRNA, attaches itself to the mRNA by complementary base pairing
  3. a second tRNA molecule attaches itself to the next codon on the mRNA in the same way
  4. ribosomal RNA (rRNA) in the ribosome catalyses the formation of a peptide bond between the two amino acids attached to the tRNA molecules
    - this joins the amino acids together
    - the first tRNA molecule moves away, leaving its amino acid behind
  5. a third tRNA molecule binds to the next codon on the mRNA
    - its amino acid binds to the first two and the second tRNA molecule moves away
  6. this process continues, producing a polypeptide chain until there’s a stop codon on the mRNA molecule
  7. the polypeptide chain moves away from the ribosome and translation is complete

A Level Biology (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions